Liquid activated color change ink and methods of use

ABSTRACT

Liquid activated ink formulations comprising a liquid activated dye, a hydrochromic ionic compound, an opacifier, and a solvent.

BACKGROUND OF THE INVENTION

The present invention is in the field of wetness/fluid indicators. Morespecifically this invention relates to wetness/fluid indicating inkwhich indicates the presence of fluid by color change. This isespecially useful in diapers, wound dressings, home construction uses,and other areas where it is desired to detect the presence of fluids.

Prior art discloses several methods for indicating wetness with a colorchange. U.S. Pat. No. 4,231,370 to Mroz et al. discloses a pHchange/color change wetness indicator which is a solid mixture dispersedin an adhesive. U.S. Pat. No. 4,022,211 to Timmons et al. discloses awater soluble coloring agent which is visible when a diaper is dry, butwhich disappears when a diaper becomes wet. U.S. Pat. No. 3,952,746 toSummers discloses the use of humidity indicator paper mounted on anabsorbent area of the diaper. U.S. Pat. No. 4,327,731 to Powelldiscloses moisture activated enzymatic systems and chromogens or pigmentproducing agents used as wetness detectors. U.S. Pat. Nos. 3,759,261 toWang and 4,192,311 to Felfoldi disclose masked color layers which becomevisible when intervening layers become wet. U.S. Pat. No. 4,931,051 toCastello discloses a wetness indicator that includes a solid hydratablesalt as an active ingredient to detect and visually signal the presenceof water.

Many pH indicators may be unreliable. The other methods disclosed arealso complicated to manufacture, as most require binding agents of somekind, and/or several manufacturing steps for implementation into afinished product

A simple, non-toxic wetness/fluid indicator is desired which would beable to be utilized with minimal manufacturing steps, for detection ofalmost any type of fluid.

SUMMARY

The liquid activated ink formulations which are utilized in thisinvention are comprised of a liquid activated dye; a hydrochromic ioniccompound; an opacifier; and a solvent. The liquid activated die is watersoluble and changes color upon coming in contact with liquid. Thisliquid activated ink may be useful in many applications including awetness indicator on diapers, wound dressings, construction, femininehygiene, and many others.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an top view of a diaper according to an aspect of theinvention.

FIG. 2 is a front view of a diaper according to an aspect of theinvention.

FIG. 3 is a cross section of diaper of FIG. 1 according to an aspect ofthe invention.

FIG. 4 is a cross section of a wound dressing according to an aspect ofthe invention.

DETAILED DESCRIPTION

Various aspects of the invention are presented in FIGS. 1-4 which arenot drawn to scale and in which like components are numbered alike.

The liquid activated ink formulations which are utilized in thisinvention are comprised of a liquid activated dye; a hydrochromic ioniccompound; an opacifier; and a solvent. The liquid activated die isliquid soluble and changes color upon coming in contact with water. Somerepresentative examples of liquid activated dyes that can be used in thepractice of this invention include: Malachite green, brilliant green,crystal violet, erythrosine B, methyl green, methyl violet 2D, picricacid, naphthol yellow S, quinaldine red, eosine Y, metanil yellow,m-cresol purple, thymol blue, xylenol blue, basis fuchsin, eosin B,4-p-aminophenol(azo)benzenesulphonic acid-sodium salt, cresol red,martius yellow, phloxine B, methyl yellow, bromophenol blue, congo red,methyl orange, bromochlorophenol blue WS, ethyl orange, flourocene WS,bromocresol green, chrysoidine, methyl red sodium salt, alizarine redS-H2O, cochineal, chlorophenol red, bromocresol purple, 4-naphtha,alizarin, nitrazine yellow, bromothymol blue, brilliant yellow, neutralred, rosalic acid, phenol red, 3-nitro phenol, orange II,phenolphthalein, o-cresolphthalein, nile blue A, thymolphthalein,aniline blue WS, alizarine yellow GG, mordant orange, tropaolin O,orange G, acid fuchsin, thiazol yellow G, and indigo carmine.

The hydrochromic ionic compound is typically a reactive ionic compound,such as an ionizing salt. Some representative examples of hydrochromicionic compounds that can be employed in the practice of this inventioninclude: lithium hydrogen sulfate, lithium hydrogen carbonate, potassiumhydrogen sulfate, potassium hydrogen carbonate, rubidium hydrogensulfate, rubidium hydrogen carbonate, cesium hydrogen sulfate, cesiumhydrogen carbonate, sodium hydrogen sulfate, sodium hydrogen carbonate,cesium hydroxide, lithium hydroxide, potassium hydroxide, calciumhydroxide, magnesium hydroxide, sodium thiosulfate penta hydrate, sodiumhydroxide, rubidium hydroxide, cobalt chloride, cobalt nitrate, coppersulpate copper nitrate, iron (II) sulfate, iron (III) sulfate, iron (II)chloride, and iron (III) chloride.

The opacifiers that can be utilized in the liquid activated inkformulations of this invention can be porosigens or antiporosigens andare typically white powders when they are in the form of dry solids(before being incorporated into the ink formulation). In the cases wherethe opacifiers act as porosigens they allow for liquid transmissionthrough coatings which are applied to a substrate, such as a coatingwhich is printed on the outer layer of a diaper. In other words, theporosigen is a compound which allows for liquid to be transmittedthrough it which facilitates liquid transmission throughout the coating.In the case of antiporosigens liquid transmission is attained by virtueof liquid permeable interstices which are formed in proximity to theantiporosigens by virtue of disrupting the structure of liquid barriermaterials. In other words, the antiporosigens cause holes to be presentin the dry coating structure which are of a size and structure whichallows for liquid to flow through the coating. Some representativeexamples of opacifiers that can be utilized include titanium dioxide,calcium carbonate, calcium hydroxide, sodium silicate, potassiumsilicate, silica, starch, ethocell, methocell, barium carbonate, bariumsilicate, calcium silicate, aluminum silicate, aluminum hydroxide, andaluminum oxide.

The solvent utilized in the liquid activated ink formulation istypically a polar solvent, such as an aqueous solvent. The solvent willnormally be water or an aqueous solution of one or more water solubleagents in water. For example, a glycol or an alcohol, such as methanol,ethanol, or isopropyl alcohol, or agents which facilitate or acceleratefilm formation can be included in the solvent.

The liquid activated ink formulation is normally prepared by simplymixing the liquid activated dye, the hydrochromic ionic compound and theopacifier into the solvent. The desired components of the liquidactivated ink formulation can be mixed together using conventional meansusing adequate shearing forces to attain an essentially homogeneousmixture. The liquid activated dye, the hydrochromic ionic compound andthe opacifier will be incorporated into the solvent at levels which areadequate to make a liquid activated ink formulation having desiredcharacteristics. For instance, the liquid activated ink formulation willbe capable of being coated onto a substrate, such as by a printingprocess, and upon drying will adhere to the surface of the substrate.The liquid activated ink formulation of this invention can be printedonto paper, non-woven fabric, woven fabric, plastic or other surfaces bysilk screen printing, flexo-printing, by application with a Myers rod,or by other suitable techniques. After drying on the substrate, the inkformulation will change color on exposure to water. The coating willpreferably change to a blue or purple color on exposure to water.

The liquid activated dye will normally be included in the liquidactivated ink formulation at a level which is within the range of about0.05 weight percent to about 20 weight percent and will generally beincorporated into the liquid activated dye at a level which is withinthe range of about 0.1 weight percent to about 15 weight percent, basedupon the total weight of the liquid activated ink formulation. Theliquid activated dye will typically be included in the liquid activatedink formulation at a level which is within the range of about 0.5 weightpercent to about 10 weight percent and will preferably be incorporatedinto the liquid activated dye at a level which is within the range ofabout 1 weight percent to about 5 weight percent.

The hydrochromic ionic compound will normally be included in the liquidactivated ink formulation at a level which is within the range of about0.05 weight percent to about 35 weight percent and will generally beincorporated into the liquid activated dye at a level which is withinthe range of about 1 weight percent to about 30 weight percent, basedupon the total weight of the liquid activated ink formulation. Thehydrochromic ionic compound will typically be included in the liquidactivated ink formulation at a level which is within the range of about10 weight percent to about 30 weight percent and will preferably beincorporated into the liquid activated dye at a level which is withinthe range of about 15 weight percent to about 25 weight percent.

The opacifier will normally be included in the liquid activated inkformulation at a level which is within the range of about 5 weightpercent to about 55 weight percent and will generally be incorporatedinto the liquid activated dye at a level which is within the range ofabout 10 weight percent to about 50 weight percent, based upon the totalweight of the liquid activated ink formulation. The opacifier willtypically be included in the liquid activated ink formulation at a levelwhich is within the range of about 20 weight percent to about 45 weightpercent and will preferably be incorporated into the liquid activateddye at a level which is within the range of about 30 weight percent toabout 40 weight percent

EXAMPLES

This invention is illustrated by the following examples which are merelyfor the purpose of illustration and are not to be regarded as limitingthe scope of the invention or the manner in which it can be practiced.Unless specifically indicated otherwise, parts and percentages are givenby weight.

Example 1

In this experiment a liquid activated ink formulation was prepared byadding 3.0 parts of bromochlorophenol blue WS, 20 parts of sodiumhydrogen carbonate, and 35 parts of aluminum silicate into 42 parts ofwater. This aqueous composition was mixed by stirring until ahomogeneous solution was attained to produce the liquid activated inkformulation.

Example 2

The liquid activated ink formulation made by the procedure delineated inExample 1 was printed onto a paper substrate using a Myers rod. Theliquid activated ink formulation was allowed to dry and exhibited goodadhesion to the substrate. After drying the coated substrate was of agenerally white color.

Water was applied to the coated substrate and it immediately turned to abrilliant blue color. Accordingly, the ink formulation which was coatedonto the paper substrate reacted to the presence of water by changingfrom a white color into an easily detectable blue color.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject invention, it will be apparentto those skilled in this art that various changes and modifications canbe made therein without departing from the scope of the subjectinvention.

Methods of Use:

According to an aspect of the invention, a disposable diaper 10 has aliquid permeable topsheet 12, a liquid impermeable backsheet 14, aliquid absorbent core 16 disposed between the topsheet 12 and thebacksheet 14 and further comprises a liquid indicator 20. The liquidindicator 20 comprises a coating 18 of liquid indicating ink disposed onthe backsheet 14, between the backsheet 14 and the absorbent core 16,such that it is visually revealed when the coating 18 is wetted withbody fluids. The liquid indicating ink is the liquid activated ink asdescribed above. This liquid indicator may change color entirely when incontact with liquid, or may change noticeable shades of color, or maychange from an almost white (so as it appears that there is no inkthere) to a color.

In prior art, there were many steps necessary for achieving liquidindicating diapers. Besides the diaper backsheet, topsheet, andabsorbent core, prior art also needed a covering layer to keep the inkin place, a surfactant, a binding agent for binding the liquid indicatorto the backsheet, and/or other items. Further, the ink used in prior artrequired a separate layer, such as maybe the ink being printed on atissue paper or the like, and then the tissue paper being placed/adheredto the backsheet.

Prior art also required surfactants for operation of the wetnessindicating diapers. The present invention can work without surfactants,although one or more surfactants may still be used.

In the present invention, the liquid indicating ink may be printeddirectly on the backsheet 14, with no binding agent, thus eliminatingthe need for extra layers, binders, covering layers and the like, andgreatly simplifying the manufacture of liquid indicating diapers.Because of the ease of manufacture by simply printing the liquidindicator on the diaper, the liquid indicator may be printed in any waydesired, such as words, shapes, numbers etc. FIG. 2 shows just oneexample of how the diaper may appear when wet, wherein the liquidindicator 20 is printed in a raindrop pattern which is visible when wet.

This liquid indicating ink lends itself to many other uses, such as usein wound dressings. According to an aspect of the invention, a wounddressing 30 comprises a contact layer 32, an absorbent dressing layer34, and an outer layer 36, and further comprises a liquid indicator 40,comprising a coating 38 of liquid indicating ink wherein the liquidindicator 40 is disposed on the outer layer 36, between the outer layer36 and the absorbent dressing layer 34. The liquid indicating ink is theliquid activated ink as described above. This liquid indicator maychange color entirely when in contact with liquid, or may changenoticeable shades of color, or may change from an almost white (so as itappears that there is no ink there) to a color. The outer layer 36should be transparent or translucent enough such that this color changeis visible through the outer layer 36. Thus when the wound seeps throughthe absorbent dressing layer to the outer layer, the color change wouldindicate it is time to change the dressing. Further, the liquidindicating ink could be printed only around the edges of the wounddressing to visibly indicate when the wound is seeping towards the edgesof the dressing.

According to a further aspect of the invention, this liquid indicatingink may be used in construction to indicate leaks or moisture. Forexample, this ink could be printed on pipe tape, such that during use,if a pipe was leaking, the color change would so indicate. Further thisink could be used in insulating materials, such as pipe insulatingmaterials. Since a pipe cannot be seen when insulated, it is difficultto determine if a pipe is leaking, or where it is leaking. If the liquidindicating ink was used in pipe insulation material, then color changewould indicate a leak, and its location.

Further, this liquid indicating ink can be made such that the colorchange is temporary, or permanent—thus if it is temporary, if a pipewith color changing insulating material is accidently exposed to liquid,through a spill for example, when the spill dries, the color wouldreturn, and the liquid indicating ink would not have lost itsusefulness.

There are many other uses in construction, such as printing on gypsumboard paper, which could indicate a leak, or moisture behind walls. As afurther example, it could be used in manufacture of dropped ceilingpanels, to indicate leaks or moisture above the dropped ceiling.

These are just a few of the example of the usefulness of this liquidindicating ink, and are not meant as an exhaustive list, as it will beapparent to those skilled in this art that various changes andmodifications can be made therein without departing from the scope ofthe subject invention. The dimensions and values disclosed herein arenot to be understood as being strictly limited to the exact numericalvalues recited. Instead, unless otherwise specified, each such dimensionis intended to mean both the recited value and a functionally equivalentrange surrounding that value. For example, a dimension disclosed as “40mm” is intended to mean “about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A liquid activated ink formulation comprising:(A) a liquid activated dye that in its dry state is colorless or white;(B) a hydrochromic ionic compound; (C) from about 5% to about 55% byweight an opacifier; and (D) a solvent.
 2. The liquid activated inkformulation as specified in claim 1 wherein the opacifier is aporosigen.
 3. The liquid activated ink formulation as specified in claim1 wherein the opacifier is an antiporosigen.
 4. The liquid activated inkformulation as specified in claim 1 wherein the liquid activated dye isselected from the group consisting of Malachite green, brilliant green,crystal violet, erythrosine B, methyl green, methyl violet 2D, picricacid, naphthol yellow S, quinaldine red, eosine Y, metanil yellow,m-cresol purple, thymol blue, xylenol blue, basis fuchsin, eosin B,4-p-aminophenol(azo)benzenesulphonic acid-sodium salt, cresol red,martius yellow, phloxine B, methyl yellow, bromophenol blue, congo red,methyl orange, bromochlorophenol blue WS, ethyl orange, flourocene WS,bromocresol green, chrysoidine, methyl red sodium salt, alizarine redS-H2O, cochineal, chlorophenol red, bromocresol purple, 4-naphtha,alizarin, nitrazine yellow, bromothymol blue, brilliant yellow, neutralred, rosalic acid, phenol red, 3-nitro phenol, orange II,phenolphthalein, o-cresolphthalein, nile blue A, thymolphthalein,aniline blue WS, alizarine yellow GG, mordant orange, tropaolin 0,orange G, acid fuchsin, thiazol yellow G, and indigo carmine.
 5. Theliquid activated ink formulation as specified in claim 1 wherein thehydrochromic ionic compound is selected from the group consisting oflithium hydrogen sulfate, lithium hydrogen carbonate, potassium hydrogensulfate, potassium hydrogen carbonate, rubidium hydrogen sulfate,rubidium hydrogen carbonate, cesium hydrogen sulfate, cesium hydrogencarbonate, sodium hydrogen sulfate, sodium hydrogen carbonate, cesiumhydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide,magnesium hydroxide, sodium thiosulfate penta hydrate, sodium hydroxide,rubidium hydroxide, cobalt chloride, cobalt nitrate, copper sulpatecopper nitrate, iron (II) sulfate, iron (III) sulfate, iron(II)chloride, and iron (III) chloride.
 6. The liquid activated inkformulation as specified in claim 1 wherein the opacifier is selectedfrom the group consisting of titanium dioxide, calcium carbonate,calcium hydroxide, sodium silicate, potassium silicate, silica, starch,ethocell, methocell, barium carbonate, barium silicate, calciumsilicate, aluminum silicate, aluminum hydroxide, and aluminum oxide. 7.The liquid activated ink formulation as specified in claim 1 wherein thea liquid activated dye is present in the liquid activated inkformulation in an amount which is within the range of about 0.05 weightpercent to about 20 weight percent, wherein the hydrochromic ioniccompound is present in the liquid activated ink formulation in an amountwhich is within the range of about 0.05 weight percent to about 35weight percent, and wherein the solvent is present in the liquidactivated ink formulation in an amount which is within the range ofabout 5 weight percent to about 55 weight percent, based upon the totalweight of the liquid activated ink formulation.
 8. The liquid activatedink formulation as specified in claim 1 wherein the liquid activated dyeis present in the liquid activated ink formulation in an amount which iswithin the range of about 0.1 weight percent to about 15 weight percent,wherein the hydrochromic ionic compound is present in the liquidactivated ink formulation in an amount which is within the range ofabout 1 weight percent to about 30 weight percent, and wherein thesolvent is present in the liquid activated ink formulation in an amountwhich is within the range of about 15 weight percent to about 50 weightpercent, based upon the total weight of the liquid activated inkformulation.
 9. The liquid activated ink formulation as specified inclaim 1 wherein the liquid activated dye is present in the liquidactivated ink formulation in an amount which is within the range ofabout 0.5 weight percent to about 10 weight percent, wherein thehydrochromic ionic compound is present in the liquid activated inkformulation in an amount which is within the range of about 10 weightpercent to about 30 weight percent, and wherein the solvent is presentin the liquid activated ink formulation in an amount which is within therange of about 25 weight percent to about 50 weight percent, based uponthe total weight of the liquid activated ink formulation.
 10. The liquidactivated ink formulation as specified in claim 1 wherein the liquidactivated dye is present in the liquid activated ink formulation in anamount which is within the range of about 1 weight percent to about 5weight percent, wherein the hydrochromic ionic compound is present inthe liquid activated ink formulation in an amount which is within therange of about 15 weight percent to about 25 weight percent, wherein theopacifier is present in the liquid activated ink formulation in anamount which is within the range of about 30 weight percent to about 40weight percent, and wherein the solvent is present in the liquidactivated ink formulation in an amount which is within the range ofabout 35 weight percent to about 45 weight percent, based upon the totalweight of the liquid activated ink formulation.
 11. The liquid activatedink formulation as specified in claim 1 wherein the solvent is a polarsolvent.
 12. The liquid activated ink formulation as specified in claim1 wherein the solvent is selected from the group consisting of water, aglycol, an alcohol, and combinations thereof.
 13. The liquid activatedink formulation as specified in claim 1 wherein the opacifier is in theform of a white particles.
 14. The liquid activated ink formulation asspecified in claim 1 wherein the opacifier is aluminum silicate.
 15. Theliquid activated ink formulation as specified in claim 13 wherein theliquid activated dye is bromochlorophenol blue WS.
 16. The liquidactivated ink formulation as specified in claim 13 wherein thehydrochromic ionic compound is sodium hydrogen carbonate.
 17. The liquidactivated ink formulation as specified in claim 1 wherein the opacifieris aluminum silicate, wherein the liquid activated dye isbromochlorophenol blue WS, wherein the hydrochromic ionic compound issodium hydrogen carbonate, wherein the solvent is water, wherein thealuminum silicate is in the form of a white particles, wherein thebromochlorophenol blue WS is present in the liquid activated inkformulation in an amount which is within the range of about 1 weightpercent to about 5 weight percent, wherein the sodium hydrogen carbonateis present in the liquid activated ink formulation in an amount which iswithin the range of about 15 weight percent to about 25 weight percent,wherein the aluminum silicate is present in the liquid activated inkformulation in an amount which is within the range of about 30 weightpercent to about 40 weight percent, and wherein the water is present inthe liquid activated ink formulation in an amount which is within therange of about 35 weight percent to about 45 weight percent, based uponthe total weight of the liquid activated ink formulation.